Android WebView: add empty jarjar ruleset.

build/jni_generator.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This file is meant to be included into a target to provide a rule
 # to generate jni bindings for Java-files in a consistent manner.
 #
 # To use this, create a gyp target with the following form:
 #  {
 #    'target_name': 'base_jni_headers',
@@ skipping 37 matching lines @@
         '<(RULE_INPUT_PATH)',
         '--output_dir',
         '<(SHARED_INTERMEDIATE_DIR)/<(jni_gen_package)/jni',
         '--optimize_generation',
         '<(optimize_jni_generation)',
         '--jarjar',
         '<(jni_generator_jarjar_file)',
       ],
       'message': 'Generating JNI bindings from <(RULE_INPUT_PATH)',
       'process_outputs_as_sources': 1,
+      'conditions': [
+        ['jni_generator_jarjar_file != ""', {
+          'inputs': [
+            '<(jni_generator_jarjar_file)',
+          ],
+        }]
+      ],
     },
   ],
   # This target exports a hard dependency because it generates header
   # files.
   'hard_dependency': 1,
 }